The present invention relates to analysis of three-dimensional (3D) medical images and, more particularly, but not exclusively to automatic analysis of 3D medical images that depicts an organ or a human body system, especially the brain, or a section thereof by identified suspected indications of different diseases or disorders.
Systems and devices for visualizing the inside of living organisms are among the most important medical developments in the last thirty years. Systems like computerized tomography (CT) scanners and magnetic resonance imaging (MRI) scanners allow physicians to examine internal organs or areas of the body that require a thorough examination. In use, the visualizing scanner outputs a 3D medical image, such as a sequence of computerized cross-sectional images of a certain body organ, which is then interpreted by specialized radiologists.
Commonly, a patient is referred for a visual scan by a general practitioner or an expert practitioner. The 3D medical image is forwarded to and diagnosed by a general radiologist who is responsible for the analysis and diagnosis of the medical image. Radiologists are trained to deal with all kinds of medical images, such as those of the brain, abdomen, spine, chest, pelvis and joints. The medical images and the diagnosis thereof are sent back to the referring practitioner. It should be noted that there are private diagnostic imaging centers (DICs) that supply radiology imaging services to whoever is interested.
In most hospitals and radiology centers, the 3D medical images are transferred to a picture archiving communication system (PACS) before being accessed by the radiologists. The PACS is installed on one or more of computers, which are dedicated for storing, retrieving, distributing and presenting the stored 3D medical images. The 3D medical images are stored in an independent format. The most common format for image storage is digital imaging and communications in medicine (DICOM).
Generally, each radiologist receives a number of 3D medical images that are required to be interpreted and diagnosed within a certain period. The radiologist usually does not know in advance which patients are at greatest risk. Therefore, the sets of 3D medical images are usually diagnosed according to a first in first out (FIFO) scheme, indications given by the referring practitioners, a random order that has been determined by the radiologist or the clinic, or a combination thereof.
The time it takes to perform a diagnosis of a 3D medical image is important as delays in diagnosis of some pathology may have a direct effect on the therapy. Today, in a typical radiology division, a delay in the diagnosis of ambulatory patients can reach several hours or even days.
It should be noted that during the last decade, the number of diagnostic tests has increased by more than 150 percent. This increase reflects a delay in the diagnoses. A number of factors drive the increase.
Firstly, improved CT and MRI scan devices are performing scans faster than ever before. The acquisition time of each scan lasts only for a few fractions of a second and the image reconstruction time has decreased from more than five seconds per image to less than three seconds per image. When dealing with the large volume sets produced by CT and MRI, seconds often add up to minutes. By performing faster scans, the throughput of the scan devices has been increased resulting in a greater number of procedures performed in a set amount of time.
As the scan procedures are quickly performed, more scan procedures are performed in a set amount of time. One example of a technological development that increases the number of scan procedures per a set amount of time is the development of the electron beam tomography (EBT) scanner. The EBT scanner is a specific form of computed axial tomography (CAT or CT) in which the X-Ray tube is not mechanically spun in order to rotate the source of X-Ray photons. Although EBT can be used for a limited number of procedures, it has no throughput limitations as it has no moving parts and therefore no scan speed limitations.
Second, these diagnostic tests are used for more applications. For example, CT scans are now commonly used for trauma patients, cardiac patients and oncology patients as well as for other radiological purposes. The expansion in breadth of applications substantially broadens the utilization of CT scans, resulting in increased utilization of the scanner. Briefly stated, this increase is an outcome of the prevalence of the CT scanners and the expansion of CT scans to new medical fields and new diagnosis procedures. Another factor for such an increase is the technological progress. One technological development that has dramatically increased the number of performed CT scans is the introduction of the multi-slice CT device. The multi-slice CT device is based on revolutionary technology and considered one of the main drivers for future market growth. The multi-slice CT device comprises multiple rows of detectors that enable the acquisition of multiple slice images per gantry rotation. The multi-slice CT device increases the number of clinical diagnostic tests per unit time. The majority of multi-slice scanners offer an increase in both the number of slices and the thinness of slices, thereby reaching even closer to true volumetric scanning. The improved scan speed has resulted in a number of single-breath hold applications that could not historically be performed on CT scanners.
Another technological development that provides clinicians with the ability to perform new diagnostic tests is a combined positron emission tomography (PET)/CT scanner. The PET/CT scanner enables clinicians to detect tumors more accurately and pinpoint their exact location in the body as the highly sensitive PET scan picks up the metabolic signal of actively growing cancer cells in the body and the CT scan provides a detailed picture of the internal anatomy that reveals the size and shape of abnormal cancerous growths. The results of the PET/CT scans are to provide combined information on both the tumor location and the metabolism. Such combined information provides a more comprehensive point of view than the information that can be extracted separately from a PET scanner or a CT scanner. As a result, the PET/CT scanner can be used for extracting information for more applications than the commonly used CT scan or PET scan.
As the demand for medical imaging scans has increased, the installed base of CT scanners, MRI scanners, and CT/PET scanners respectively increased. For example, CT scan devices are now installed in more hospitals and freestanding imaging centers. Moreover, the number of mobile imaging services as well as cardiac and preventive screening centers that provide CT scan services has dramatically increased. It should be noted that the average number of CT scan devices in each installed base has also increased in the last decade.
As a result of the abovementioned reasons, the demand for radiologists substantially increases. Unfortunately, the supply of radiologists has not keep up with the demand and there is a growing shortage of several thousands in the number of well-trained, qualified radiologists only in the US.
During the last years, few developments have been conceived in order to increase the throughput of radiologists and in order to improve their diagnoses. Most of the developments are related to the field of computer aided detection (CAD) systems. CAD systems assist radiologists in detecting cancerous tissue after an initial diagnostic imaging screening procedure is performed. The CAD systems are used most often in mammography and recently in the diagnosis of lungs and intestine.
In practice, CAD is applied in the following fashion. A patient arrives at an imaging facility. A technologist uses imaging equipment to create medical images. These images are then forwarded to a CAD system. The CAD system analyzes the images and provides a visual representation of the images, marking potentially suspicious regions on a paper or an electronic display. Subsequently, when the radiologist is reading the images for the patient, the CAD outputs are examined in order to provide potential new areas for consideration. The utility of CAD is in prompting a radiologist to consider areas and specific region of interests (ROI) not initially detected in the first analysis of the images. Clearly, the CAD system is used as a tool intended to aid a radiologist in his or her diagnosis and not to replace them. Such tools are commonly known as second reader or second viewer. It should be noted that some CAD systems have been approved by the food and drug administration (FDA) to replace one physician in procedures that require diagnosis of two physicians.
Though the CAD system aids radiologists during the diagnosis process, the aforementioned throughput problems and the delays remain unchanged. Moreover, none of the known CAD systems is designed to aid in a general diagnosis of the brain.
Developments have been made in order to improve the workflow of radiologists using CAD systems. For example, Patent Application No. 2005/0123185A1 published on Jun. 9, 2005 describes such a method and a system. The method includes a number of steps: (a) accessing an image case, the image case comprises one or more digital images; (b) identifying a view orientation for each of the one or more digital images; (c) transmitting the image case to an algorithm server for processing of each of the one or more digital images to generate a CAD report for the image case; (d) providing a report system adapted to organize a plurality of CAD reports wherein each of the CAD reports are selectable by an operator for viewing; (e) automatically transmitting the CAD report to the report system; (f) allowing the operator to select the CAD report for viewing; and (g) displaying the selected computer aided detection report on the display.
Though such a system can improve the workflow, the delays in the diagnosis process are not substantially decreased, inter alia, because the order of the received 3D medical images remains constant.
Other known CAD systems are usually designed to aid radiologists in the diagnosis of mammographic images. For example, Patent Application No. 2006/0222228A1 published on Oct. 5, 2006 describes a method and system adapted to analyze a radiograph for bone mineral density screening and mammography computer aided detection. The method for analyzing a radiograph includes the following steps: providing a digital image based on the radiograph; determining whether a radiographic absorptiometry analysis or computer aided detection analysis is desired; and performing a radiographic absorptiometry analysis or computer aided detection analysis on the digital image based on the desired determination. The system can include an input station, a report station, and a printer.
Though such CAD systems improve the quality of each analysis, they fail to improve the throughput of the diagnosis. Moreover, most of the known CAD systems are designed to aid radiologists in diagnosis of mammographic images or other indication-specific images, and some of the known CAD systems are designed for other market segments. Examples for such market segments are chest-lung diagnosis and virtual colonoscopy diagnosis.
Though aiding in the detection process, the currently used CAD systems do not overcome the difficulties in the current diagnosis workflow of medical images. Moreover, the currently used CAD systems do not aid in the detection of indications in some market segments such as brain MRI scans, brain CT scans etc.
There is thus a widely recognized need for, and it would be highly advantageous to have, a system and a method for overcoming the aforementioned difficulties devoid of the above limitations.